Method and apparatus for determing the coronary sinus vein branch accessed by a coronary sinus lead

ABSTRACT

Systems and methods for determining the coronary sinus vein branch location of a left ventricle electrode are disclosed. The systems and methods involve detecting the occurrence of electrical events within the patient&#39;s heart including sensing one or more of the electrical events with the electrode and then analyzing the electrical events to determine the electrode&#39;s position. The determination of electrode position may be used to automatically adjust operating parameters of a VRT device. Furthermore, the determination of electrode position may be made in real-time during installation of the electrode and a visual indication of the electrode position may be provided on a display screen.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/976,397, filed Dec. 22, 2010, which is a continuation of U.S.application Ser. No. 11/834,484, filed Aug. 6, 2007, now U.S. Pat. No.7,881,794, which is a divisional of U.S. application Ser. No.10/729,301, filed Dec. 5, 2003, now U.S. Pat. No. 7,260,427, which is adivisional of U.S. application Ser. No. 09/822,638, filed Mar. 30, 2001,now U.S. Pat. No. 6,705,999, all of which are incorporated herein byreference in their entirety for all purposes.

TECHNICAL FIELD

The present invention relates to ventricular resynchronization therapy(VRT) devices. More specifically, the present invention relates todetermining a coronary vein branch position of the coronary sinus leadof a VRT device.

BACKGROUND

Ventricular resynchronization therapy is one method of treating heartfailure patients. VRT often requires that the left ventricle of apatient be electrically stimulated. This is especially true if there isa conduction disorder in the left ventricle of the heart whereby thefast conductivity fibers (i.e., pumping system) in the left ventricleare damaged. When the conduction fibers are damaged, electrical wavestraveling through the heart no longer travel quickly through the highspeed fibers but instead travel much slower as they pass sequentiallythrough muscle conduction. This slowing of the wave propagation throughthe left ventricle may cause one part (usually the septum) of theventricle to contract first and begin to relax before another part(usually the freewall) of the ventricle contracts.

One scenario is that the freewall of the ventricle tends to expandduring the period of contraction of the septum. Once the freewall beginsto contract, the septum has relaxed. As a result of the septum andfreewall portions contracting at different times, blood is passedside-to-side within the ventricle rather than being efficiently pumpedout into the arteries.

VRT attempts to improve the pumping efficiency of the heart by providingan electrical stimulation to a later contracting part of the ventricle,for example the freewall, contemporaneously with the natural contractionof the earlier contracting portion, such as the septum. Because bothsides contract at approximately the same time with VRT, the volume ofthe left ventricle is significantly reduced and blood is effectivelypumped out into the arteries. To provide such electrical stimulation, anelectrode connected to a VRT device must be positioned near the delayedregion of the ventricle. The delayed region may be accessed via a branchof the coronary sinus vein that extends over the portions of the leftventricle.

The most accessible branches of the coronary sinus vein include thelateral, posterior, and anterior branches. Creating an electricalstimulation in the lateral or posterior branch provides the besthemodynamic response and maximizes the benefit from VRT for patientswith left ventricle conduction disorder. Therefore, it is desirable toplace the electrode of the VRT device in the lateral or posterior branchinstead of the anterior branch. Furthermore, the timing of theelectrical impulse provided by the VRT device to the electrode must beset according to the position of the electrode to induce contraction ofthe delayed portion of the ventricle at the appropriate time. Thus, thelocation of the electrode must be known.

During installation of the electrode, fluoroscopy is used to determinethe position of the lead, and fluoroscopy exposes the patient to X-rayradiation. If the patient has an abnormal coronary sinus vein system,then fluoroscopy may become unreliable in determining the location ofthe electrode. Additionally, unusual anatomy may require a longerfluoroscopy exposure time. Thus, using fluoroscopy to determineelectrode position during installation has drawbacks.

Thus, it is desirable to provide a method and system that enables theposition of the electrode in the left ventricle to be determined withoutor in addition to fluoroscopy, to automatically configure the VRT devicebased on the detected position, and to display in real-time the detectedposition on a video display.

SUMMARY

Embodiments of the present invention assist in installation and/or setupand identification of an electrode in the left ventricle area of apatient's heart. These embodiments involve detecting electrical eventsin the patient's heart and then determining the position of the leftventricle (LV) electrode from measurements of the electrical events.

The present invention may be viewed as a method for determining aposition of a first electrode placed within a left ventricle area of apatient's heart. The method involves detecting a first depolarizationevent within the heart and sensing, with the first electrode, a seconddepolarization event within the heart. The method further involvesmeasuring a first interval between the first depolarization event andthe second depolarization event and determining from at least the firstinterval whether the lead has a lateral/posterior position or ananterior position within the left ventricle.

The present invention may be viewed as another method for determining aposition of an electrode within a left ventricle of a patient's heart.This method involves detecting a first depolarization event within theheart and sensing, with the electrode, a second depolarization eventwithin the heart. The method also involves measuring a first intervalbetween the first depolarization event and the second depolarizationevent and detecting a third depolarization event within the heart. Asecond interval is measured between the third depolarization event andthe second depolarization event, and the electrode position isdetermined based on an evaluation of the first and the second intervals.

The present invention may be viewed as a system for determining theposition of a first electrode in a left ventricle area of a patient'sheart. The system includes one or more detection devices for detectingat least first and second electrical events in the patient's heart, oneof the one or more detection devices being electrically connected to thefirst electrode and detecting the second electrical event in the leftventricle area. The system also includes a processing device inelectrical communication with the one or more detection devices. Theprocessing device is configured to calculate a first interval betweenthe first and second electrical events and determine the position of theelectrode based at least upon the first interval.

The present invention may be viewed as another system for determiningthe position of a first electrode in a left ventricle area of apatient's heart. This system includes means for detecting a firstelectrical event within the patient's heart, means for detecting asecond electrical event occurring at the first electrode, and means fordetermining whether the first electrode has an anterior orlateral/posterior position within the left ventricle based at least on afirst interval between the first and second electrical events.

The present invention may be viewed as a method for assistinginstallation of an electrode in a lea ventricle of a patient's heart.This method involves placing the electrode in a coronary sinus veinbranch of the left ventricle and detecting a plurality of electricalevents in the patient's heart during a heart beat, wherein at least oneof the plurality of electrical events is sensed by the electrode. Themethod also involves determining from the plurality of electrical eventswhether the electrode has an anterior or a lateral/posterior vein branchposition during the heart beat and displaying on a display screen anindication of the determined position of the electrode.

The present invention may be viewed as a method for assistinginstallation of an electrode of a VRT device in a left ventricle of apatient's heart. The method involves placing the electrode in a coronarysinus vein branch of the left ventricle and detecting a plurality ofelectrical events in the patient's heart during a heart beat, wherein atleast one of the plurality of electrical events is sensed by theelectrode. The method also involves determining from the plurality ofelectrical events whether the electrode has an anterior or alateral/posterior vein branch position during the heart beat andadjusting settings used by the VRT device based upon the determinedposition of the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a typical human heart with locations for placement ofelectrical leads in accordance with embodiments of the presentinvention.

FIG. 2 shows an intracardiac electrogram measured by an electrode withinthe left ventricle and a Q*R_(L) interval measurement.

FIG. 3 shows an intracardiac electrogram measured by an electrode withinthe right ventricle in relation to an intracardiac electrogram measuredon the same beat by an electrode within the left ventricle and anR_(R)R_(L) interval measurement.

FIG. 4 depicts electrical lead and electrode placement within the heartand detection of the intracardiac electrogram signals from theelectrodes.

FIG. 5 illustrates the operational flow of an embodiment of the presentinvention where the VRT device settings are automatically adjusted inresponse to determination of electrode position within the leftventricle using one or more interval measurements and a probabilityrule.

FIG. 6 depicts the operational flow of an embodiment of the presentinvention where the electrode position, determined using one or moreinterval measurements and a probability rule, is provided to a displayin real-time during the installation of the left ventricle electrode inthe patient.

FIG. 7 shows the operational flow of an embodiment of the presentinvention where the VRT device settings are automatically adjusted inresponse to determination of electrode position within the leftventricle using single or multiple interval threshold comparison.

FIG. 8 depicts the operational flow of an embodiment of the presentinvention where the electrode position, determined using single ormultiple interval threshold comparison, is provided to a display inreal-time during the installation of the left ventricle electrode in thepatient.

DETAILED DESCRIPTION

Various embodiments of the present invention will be described in detailwith reference to the drawings, wherein like reference numeralsrepresent like parts and assemblies through the several views. Referenceto various embodiments does not limit the scope of the invention, whichis limited only by the scope of the claims attached hereto.

Embodiments of the present invention assist in the installation and/orsetup of an electrode in the coronary sinus vein branches of the leftventricle area of a patient's heart. These embodiments provide systemsand methods that may be used in place of or as a supplement tofluoroscopy. Furthermore, certain of these embodiments provide methodsand systems for providing automatic adjustment of VRT settings that arebased on the electrode position and are necessary for proper stimulationof the left ventricle. Certain of these embodiments also provide methodsand systems for providing real-time indication of the electrode positionduring electrode installation to assist in providing the most beneficialplacement of the electrode.

FIG. 1 illustrates a typical human heart 100. The heart 100 has fourchambers including a right atrium area 102, a left atrium area 108, aright ventricle area 104, and a left ventricle area 106. Operation ofVRT devices typically requires placement of an electrode in an atriumarea such as 118. An electrode is also typically placed in a rightventricle apex area such as 116. Embodiments of the present inventionare directed to determining the placement of an electrode in the leftventricle area.

The electrode for the left ventricle area is generally inserted throughthe coronary sinus vein into one of the three most accessible branchesspanning the surface of the ventricle including the anterior branch, theposterior branch, and the lateral branch. The anterior branch typicallyspans the anterior area 114. For patients with a left bundle branchdisorder which affects the conduction to the freewall of the leftventricle, placing the electrode in this anterior area 114 is leastbeneficial because it lies too closely to the septum of the leftventricle 106 and does not most effectively enhance the coordination ofthe left ventricle's contractions.

The posterior branch of the coronary sinus vein spans posterior area112. Placing the electrode in this area allows the left ventriclefreewall to be efficiently contracted in coordination with thecontractions of the septum. The lateral branch of the coronary sinusvein spans lateral area 110. As with the posterior position, placing theelectrode in the lateral area allows the freewall of the left ventricle106 to be efficiently contracted in coordination with the septum aswell. Thus, it is desirable to place the electrode in the posterior area112 or the lateral area 110. These areas will be referred to together asthe lateral/posterior position.

Embodiments of the present invention require detection of electricalevents within the heart. Thus, the electrodes placed into the heart,including the electrode in the coronary sinus vein branch, sense thenaturally occurring depolarization of the cells as the electrical wavetravels by the electrode as it moves down the surface of the heart fromthe atrium area to the ventricle area. FIG. 2 shows an intracardiacelectrogram signal 200 of the left ventricle that is sensed by theelectrode being inserted through the coronary sinus vein. As theelectrical activation begins in the ventricle, the electrode senses anelectrical depolarization event such as onset (Q*) 202 of the QRScomplex. The QRS complex is the electrical depolarization activity thatoccurs in the ventricles of the heart as the electrical wave propagatesthrough the ventricles. After the onset (Q*) 202, when the electricalwave passes by the electrode, another electrical depolarization eventsuch as the peak (R_(L)) 204 of the QRS complex is sensed.Alternatively, the maximum negative derivative of the R wave may besensed in place of the peak value.

The electrode being inserted into the left ventricle area senses anelectrogram signal 200 of FIG. 2 regardless of whether it is positionedin the anterior or lateral/posterior position. However, the interval(Q*R_(L)) between the onset (Q*) 202 and the peak (R_(L)) 204 changesdepending upon the electrode's position because the time of sensing theonset (Q*) 202 is not significantly affected by the position of theelectrode but the time of sensing the peak (R_(L)) 204 is so affected.The interval (Q*R_(L)) is smaller if the electrode lies in the anteriorposition than it is if the electrode lies in the lateral/posteriorposition. Therefore, this interval may be computed and relied upon todetermining the electrode's position.

FIG. 3 shows an intracardiac electrogram signal 300 sensed by anelectrode placed in a right ventricle location 116 in relation to theintracardiac electrogram signal 302 sensed by the left ventricleelectrode. The right ventricle electrode senses an electricaldepolarization event such as the peak (R_(R)) 304 of the QRS complex asthe electrical wave passes by. The occurrence of this peak (R_(R)) 304is not affected by the placement of the left ventricle electrode, butthe occurrence of the QRS complex peak (R_(L)) 306 is affected by theplacement. Therefore, this peak (R_(R)) 304 may be used as a referencepoint for measuring the relative timing of the peak (R_(L)) 306 of theQRS complex detected by the left ventricle electrode. The interval(R_(R)R_(L)) between the two peaks may also be computed and relied uponto determine the electrode's position.

A-wave electrical depolarization activity (A) detected by an electrodein the atrium area such as 118 is also unaffected by the placement ofthe left ventricle electrode. Therefore, A-wave activity detected by theatrial electrode may also be used as a reference marker for determiningthe timing of the left ventricle electrode sensing the peak R_(L) of theQRS complex. However, because the delay from the transition of theelectrical wave from the atrium area to the ventricle area (A/V delay)may significantly vary from one patient to the next, it is generally notas accurate to determine left ventricle (LV) electrode position based onan interval (A R_(L)) measured from the occurrence of atrial activity(A) to the occurrence of the peak (R_(L)) 306 of the QRS complexdetected by the left ventricle electrode.

Whether using the interval (Q*R_(L)), the interval (R_(R)R_(L)), or theinterval (A R_(L)), the position of the electrode may be detected bycomparing the interval to a threshold value determined empirically. Ithas been found that 100 ms and shorter Q*R_(L) intervals generallyindicate an anterior position in humans. It has also been found that 50ms and shorter R_(R)R_(L) intervals generally indicate an anteriorposition in humans. Rather than using a single interval, both theinterval (Q*R_(L)), and the interval (R_(R)R_(L)), may be computed andused to determine lead position. The sum of both intervals may becompared to a threshold, such as 150 ms for humans where 150 ms andshorter interval sums indicate an anterior position. Alternatively, bothintervals may be statistically combined to find the probability of theelectrode being in the anterior or the lateral/posterior position. Ithas been empirically determined that in humans, the following equationsprovide a reliable basis for determining position.

d_(A) = 0.004(Q * R_(L) + R_(R)R_(L) − 100)², d_(L) = 0.004(Q * R_(L) + R_(R)R − L − 200)², and$P = {\frac{\exp( {{- 0.5}d_{A}} )}{{\exp( {{- 0.5}d_{A}} )} + {\exp( {{- 0.5}d_{L}} )}} = \frac{1}{1 + {\exp\lbrack {{- 0.5}( {d_{L} - d_{A}} \rbrack} }}}$

where d_(A) is the approximation of the probability density function ofthe electrode being in the anterior position,

where d_(L) is the approximation of the probability density function ofthe electrode being in the lateral/posterior position,

where P is the probability of the electrode being in the anteriorposition, and

where Q*R_(L) and R_(R)R_(L) values are in milliseconds.

The single parameter Q*R_(L) may be used to determine electrode locationwith a probability classification rule, rather than a direct intervalthreshold comparison, such as whered _(A)=0.001(Q*R _(L)−70)², andd _(L)=0.001(Q*R _(L)−130)²

-   -   with Q*R_(L) expressed in milliseconds.

An anterior position is determined for a resulting probability value Pof greater than or equal to 0.5.

The single parameter R_(R)R_(L) may be used to determine electrodelocation with a probability classification rule, rather than a directinterval threshold comparison, such as whered _(A)=0.0005(R _(R) R _(L)−20)²,andd _(L)=0.0005(R _(R) R _(L)−80)²

-   -   with R_(R)R_(L) expressed in milliseconds.

An anterior position is determined for a resulting probability value Pof greater than or equal to 0.5.

For each of these probability classification rules, when P is equal toor greater than 0.5, then the position of the electrode is determined tobe in an anterior position. Otherwise, the electrode is determined to bein the lateral/posterior position. Thus, the location of the electrodemay be found by providing a device whose operations include sensingelectrical events in the heart including an electrical event sensed bythe LV electrode, measuring the intervals between the events, and thenanalyzing the intervals to find the electrode position.

The above-described classification rules based on the likelihoodfunction P have been derived from a complex linear discriminant functionthat numerically maximizes the distance between the mean value from theQ*R_(L) set and the mean value from the R_(R)R_(L) set measured atimplants from electrodes with known anterior and lateral/posteriorpositions. Electrode position was measured in 69 patients with 104 totalelectrode positions. Thirty-seven patients had a single set of intervalmeasurements and the remaining 32 patients had interval measurementstaken at different electrode positions.

The above-described classification rules were validated by randomlyselecting one set of measurements per patient to form training data. Theremaining sets of measurements formed the test data. Statisticaldiscriminant analysis was used to analyze the training and test data inaddition to using the classification rules for P. Table A below showsthe overall sensitivity (classification of lateral/posterior positioncorrectly) and specificity (classification of anterior positioncorrectly) estimated by using the classification rule for P utilizingboth the Q*R_(L) and the R_(R)R_(L) parameters and estimated by usingthe statistical discriminant analysis after 10,000 iterations.

TABLE A Test data, Training data, Test data, Training data,classification classification discriminant discriminant rule for P rulefor P analysis analysis Sensitivity 80.7% 76.9% 79.4% 77.6% Specificity90.9% 92.0% 90.6% 89.1%

It can be seen from the cross-validation that the classification rulefor P based on both the Q*R_(L) and the R_(R)R_(L) parameters candetermine electrode position. The accuracy of the classification ruleabove for P is comparable to that obtained by regular discriminantanalysis, as indicated by Table A.

Table B shows the results of using the same patients and measurementswhile applying the single parameter Q*R_(L) classification rule. Theaccuracy of the classification rule is comparable to that obtained byregular discriminant analysis.

TABLE B Test data, Training data, 100 ms 100 ms threshold threshold Testdata, Training data, classification classification discriminantdiscriminant rule rule analysis analysis Sensitivity 77.9% 78.0% 77.3%76.0% Specificity 88.2% 84.3% 90.9% 86.8%

Table C shows the results of using the same patients and measurementswhile applying the single parameter R_(R)R_(L) classification rule. Theaccuracy of this classification rule is also comparable to that obtainedby regular discriminant analysis.

TABLE C Test data, Training data, 50 ms 50 ms threshold threshold Testdata, Training data, classification classification discriminantdiscriminant rule rule analysis analysis Sensitivity 80.8% 76.9% 82.1%77.8% Specificity 90.8% 92.1% 90.9% 92.0%

The probability classification rules mentioned above have been designedto produce the probability of the electrode having an anterior position.The probability classification rule could be altered so as to producethe probability of the electrode having a lateral/posterior positioninstead by replacing d_(A) in the numerator with d_(L). However, alateral/posterior position would be concluded only where P is greaterthan 0.5 and an anterior position would be concluded where P is 0.5 orless. It is desirable to conclude that the electrode is in an anteriorposition when P=0.5, for either definition of P, to be cautious.

The embodiments of the operations of the invention utilizing detectionof electrical events and threshold or classification rule comparisonsdescribed herein, such as but not limited to those of FIGS. 4-8, areimplemented as logical operations in the system. The logical operationsare implemented (1) as a sequence of computer implemented steps runningon a computer system, such as a device programmer or the implantable orexternal VRT device itself, comprising a processing module and/or (2) asinterconnected machine modules running within the computing system.

This implementation is a matter of choice dependent on the performancerequirements of the computing system implementing the invention.Accordingly, the logical operations making up the embodiments of theinvention described herein are referred to as operations, steps, ormodules. It will be recognized by one of ordinary skill in the art thatthe operations, steps, and modules may be implemented in software, infirmware, in special purpose digital logic, analog circuits, and anycombination thereof without deviating from the spirit and scope of thepresent invention as recited within the claims attached hereto.

FIG. 4 shows the configuration of the electrodes and electrical leadstransferring signals from the electrodes to amplification, detection,and processing modules as would be the case during installation of theLV electrode 406. FIGS. 5-8 show exemplary processing operations of theprocessing module 424 that operate in conjunction with the configurationshown in FIG. 4. The heart 402 of FIG. 4 has an atrial electrode 408, aright ventricle (RV) electrode 404, and an LV electrode 406. The LVelectrode 406 may be in the process of being installed by a surgeonwhile the operations of FIGS. 4-8 are occurring.

The atrial electrode 408 has leads connected to an amplifier 412 thatboosts the signal sensed by the electrode to improve the signal to noiseratio before the signal is provided to reference marker detection module412. The RV electrode 404 has leads connected to an amplifier 410 thatboosts its signal before being provided to depolarization detectionmodule 416. The LV electrode 406 has leads connected to an amplifier 414that boosts its signal before being provided to depolarization detectionmodule 420.

Reference marker detection module 412 may utilize existing circuitry ina VRT device or a VRT device programmer telemetered to the VRT device todetect the A-wave reference activity (A). Detection module 416 mayutilize existing peak detector circuitry in a VRT device or VRT deviceprogrammer to detect the peak (R_(R)) of the QRS complex at the RVelectrode 402. Likewise, detection module 420 may utilize existing peakdetector circuitry in a VRT device or VRT device programmer to detectthe peak (R_(L)) of the QRS complex at the LV electrode 406. If the QRScomplex onset (Q*) as sensed by the LV electrode is to be used, thewaveform including the QRS complex must be acquired and analyzed, suchas by the detection module 420 of the VRT device or VRT deviceprogrammer. The values determined by the detection modules are passed tothe processing module 424 for analysis.

The acquisition involves digitizing the waveform including the activitybeginning at the time of the atrial reference marker and extendingbeyond the QRS complex received by the LV electrode 406 and storing itin memory of the VRT device or VRT device programmer. Then, theprocessing module may find Q such as by the following process.

First, the detection module 420 smoothes the waveform V(n). This may bedone by smoothing the waveform V(n) seven times using a 5 pointrectangular moving window (for a sampling frequency of 500 Hz) wherebythe 5 samples for each window are averaged and the average is assignedto the middle sample of the five. A derivative dV(n)/dt of the smoothedwaveform is taken, and the absolute value of the derivative dV(n)/dt isnormalized to range from 0 to 1.

The time samples n from the atrial reference marker time T_(P) to thetime T_(R) of the peak (R_(L))of the R wave of the QRS complex areanalyzed. This analysis involves calculating the mean and standarddeviation of both the smoothed waveform V(n) and the normalized absolutevalue of its derivative dV(n)/dt for each time sample within a 50 msmoving window. The window with the minimum mean plus standard deviationfor |dV(n)/dt| is found and its values are used in the following steps.

For each sample n between T_(P) and T_(R), if the mean for |dV(n)/dt|within this window is less than |dV(n)/dt|, and if |dV(n-1)/dt| is lessthan or equal to the mean for |dV(n)/dt|, then the number of data pointsN in another 50 ms window is found. N is the accumulation of each datapoint where |dV(nw)/dt| is greater than the mean of |dV(n)/dt| plus thestandard deviation of |dV(n)/dt|. The window sample nw of this otherwindow ranges from n to n plus the total number of data points in thewindow.

If N divided by the total number of data points in the window is greaterthan 0.96 and T_(q)=0, then set T_(q) equal to n0-1, where T_(q), is thecurrent result of sample time for Q* and n0 is the time sample of thefirst data point that contributes to N. If the total number of datapoints in the window minus N is greater than or equal to 2, then T_(q)is reset to zero. After this is completed for all values of n betweenT_(p) and T_(R), then the final value of T_(q) is used as Q*. Thisprocess may be repeated to obtain a value of Q* for several beats, suchas 16, and the median of these Q* values may be used in theabove-mentioned classification rules. It may be desirable to include Q*values in the median determination for beats where the interval from Rwave peak to R wave peak between beats has a variation within 10%.

In certain embodiments, the output circuitry module 422 receives VRTsettings as automatically determined by the processing module 424 fromoperations such those as shown in FIGS. 5 and 7. Otherwise, outputcircuitry module 422 may receive VRT settings as entered manually afterdetermination of the LV electrode position. The output circuitry module422 provides timed electrical pulses to the electrical leads connectedto the RV electrode 404 and the LV electrode 406 to cause theseelectrodes to stimulate the ventricles at specified times during normaloperation. The video display 426 receives signals from the processingmodule 424 that cause the video display 426 to display an indication ofLV electrode position that can be viewed by the surgeon in real-time.

FIG. 5 illustrates one example of the processing operations ofprocessing module 424 that receives the detection of electrical eventsin the heart from detection modules of FIG. 4 to automatically set theVRT device for proper operation based on the LV electrode position. Thisexample may utilize the previously discussed statistical combination ofthe interval (Q*R_(L))and the interval (R_(R)R_(L)),or it may utilize asingle interval. At calculate operation 502, the interval(Q*R_(L))and/or the interval (R_(R)R_(L)) are calculated from valuesfound by the detection operations 416 and 420. Query operation 504 thendetects whether the two intervals are valid by comparison to standardlimits for each. Thus, if either of the two intervals is too short ortoo long to be accurate, then resample operation 506 triggers thedetection modules 416 and 420 to resample the electrical events foranother measurement. Valid ranges for humans are approximately 0 to 500ms for (Q*R_(L)) and −200 to 500 ms for (R_(R)R_(L)).

If query operation 504 detects valid intervals, then probabilityoperation 508 computes the values d_(A), d_(L), and P using a singleinterval or both. Computing P may involve mathematical application ofthe desired equation for P to the measured intervals or may involvelooking up the value of P in a table stored in memory of the VRT deviceor programmer. Query operation 510 then tests whether P is greater thanor equal to 0.5. If so and P is defined as the probability of anteriorposition, then position operation 514 sets the position in the VRTdevice and/or programmer as anterior. If query operation 510 detectsthat P is less than 0.5, then position operation 512 sets the positionin the VRT or programmer as lateral/posterior. Based on setting theposition as anterior or lateral/posterior, parameter operation 516 setsthe VRT parameters such that the timing used by output circuitry module422 to send a pulse to the LV electrode accounts for the LV electrodeposition.

FIG. 6 illustrates an example of the processing operations of processingmodule 424 that receives the detection of electrical events in the heartfrom detection modules of FIG. 4 to provide a visual indication on adisplay screen of the LV electrode position. This visual display may beprovided in real-time during installation of the LV electrode on abeat-by-beat basis. This example also utilizes the previously discussedstatistical combination of the interval (Q*R_(L)) and the interval(R_(R)R_(L)),or it may utilize a single interval. At calculate operation602, the interval (Q*R_(L)) and/or the interval (R_(R)R_(L)) arecalculated from values found by the detection modules 416 and 420. Queryoperation 604 then detects whether the two intervals are valid bycomparison to standard limits for each. Thus, if either of the twointervals is too short or too long to be accurate, then resampleoperation 606 triggers the detection modules 416 and 420 to resample theelectrical events from another heart beat.

If query operation 604 detects valid intervals, then probabilityoperation 608 computes the values d_(A), d_(L), and P, using a singleinterval or both. Query operation 610 then tests whether P is greaterthan or equal to 0.5. If so and P is defined as the probability ofanterior position, then position operation 614 sets the position in theVRT device and/or programmer as anterior. If query operation 610 detectsthat P is less than 0.5, then position operation 612 sets the positionin the VRT or programmer as lateral/posterior. Based on setting theposition as anterior or lateral/posterior, display operation 616 sends avisual indication to a display screen 426 indicating the LV electrodeposition. The visual indication may be a display of the calculatedintervals of operation 602 or it may simply indicate anterior orlateral/posterior. After updating the visual indicator at displayoperation 616, operational flow transitions to resample operation 606where the detection modules of FIG. 4 sense the electrical events on thenext heart beat and provide the detected values back to calculateoperation 602 for another iteration.

FIG. 7 illustrates another example of the processing operations ofprocessing module 424 that receives the detection of electrical eventsin the heart from detection modules of FIG. 4 to automatically set theVRT device for proper operation based on the LV electrode position. Thisexample utilizes single or multiple interval threshold comparison wherethe value to compare against the threshold may be the interval(Q*R_(L)),the interval (R_(R)R_(L)),the interval (A R_(L)),or a sum oftwo or all three intervals. At calculate operation 702, the desiredinterval(s) are calculated from values found by one or more of thedetection operations 412, 416, and 420. Query operation 704 then detectswhether the intervals are valid by comparison to standard limits foreach. Thus, if any of the intervals is too short or too long to beaccurate, then resample operation 706 triggers the detection modules412, 416, and/or 420 to resample the electrical events from anotherheart beat.

If query operation 704 detects valid intervals, then query operation 708tests whether the interval or sum of intervals exceeds the thresholdstored in memory of the processing module 424. As mentioned, anempirically determined threshold that is reliable for humans is about100 ms for (Q*R_(L)) and 50 ms for (R_(R)R_(L)) or 150 ms if using thesum of both intervals for comparison to the threshold. If the thresholdis not exceeded, then position operation 712 sets the position in theVRT device and/or programmer as anterior. If query operation 708 detectsthat the interval does exceed the threshold, then position operation 710sets the position in the VRT or programmer as lateral/posterior. Basedon setting the position as anterior or lateral/posterior, parameteroperation 714 sets the VRT parameters such that the timing used byoutput circuitry module 422 to send a pulse to the LV electrode accountsfor the LV electrode position.

FIG. 8 illustrates another example of the processing operations ofprocessing module 424 that receives the detection of electrical eventsin the heart from detection modules of FIG. 4 to provide a visualindication on a display screen of the LV electrode position. As with theoperations of FIG. 6, this visual display may be provided in real-timeduring installation of the LV electrode on a beat-by-beat basis. Thisexample utilizes single or multiple interval threshold comparison wherethe value to compare to the threshold may be the interval (Q*R_(L)),theinterval (R_(R)R_(L)), the interval (A R_(L)),or a combination thereof.At calculate operation 802, the desired interval is calculated fromvalues found by one or more of the detection operations 412, 416, and420. Query operation 804 then detects whether the two intervals arevalid by comparison to standard limits for each. Thus, if either of thetwo intervals is too short or too long to be accurate, then resampleoperation 806 triggers the detection modules 412, 416, and/or 420 toresample the electrical events from another heart beat.

If query operation 804 detects valid intervals, then query operation 808tests whether the interval exceeds the threshold stored in memory of theprocessing module 424. If not, then position operation 812 sets theposition in the VRT device and/or programmer as anterior. If queryoperation 808 detects that the interval does exceed the threshold, thenposition operation 810 sets the position in the VRT or programmer aslateral/posterior. Based on setting the position as anterior orlateral/posterior, display operation 814 sends a visual indication to adisplay screen 426 indicating the LV electrode position. The visualindication may be a display of the calculated intervals of operation 802or it may simply indicate anterior or lateral/posterior. After updatingthe visual indicator at display operation 816, operational flowtransitions to resample operation 806 where the detection modules ofFIG. 4 sense the electrical events on the next heart beat and providethe detected values back to calculate operation 802 for anotheriteration.

The operations of FIGS. 5 and 6 or 7 and 8 may be combined such that areal-time visual indication of the LV electrode position is shown on adisplay screen 426 and the VRT settings for output circuitry 422 areautomatically adjusted based on the determined position. As mentioned,embodiments may employ the amplification, detection, and processingmodules of FIG. 4 and operations of FIGS. 5

8 in an external VRT device, an implantable VRT device, or a VRT deviceprogrammer telemetered to the VRT device connected to the leads.Furthermore, embodiments may employ some of the modules and/oroperations in the VRT device while employing others in the programmer.

Once the LV electrode is in a satisfactory position, as may have beendetermined by the surgeon viewing the display screen 426 whileinstalling the LV electrode, the settings for the VRT device may bemanually or automatically adjusted as discussed above. At that time, theprocessing operations of the present invention may terminate. Theprocessing operations of the present invention may later be re-invokedto determine the LV electrode position or update the VRT settings infollow-up visits.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various other changes in the form anddetails may be made therein without departing from the spirit and scopeof the invention.

We claim:
 1. A system for determining the position of an electrode in apatient's heart, the system comprising: an electrode; and a processingdevice configured to receive a first cardiac electrical signalrepresentative of a first electrical event sensed by the electrode overa time window spanning a plurality of heartbeats and a second cardiacelectrical signal representative of a second electrical event sensed bythe electrode over the time window, and to calculate a position of theelectrode in or near the heart based at least in part upon an averagetime interval between the first and second electrical events occurringduring each heartbeat within the time window.
 2. The system of claim 1,wherein the processing device is configured to determine, based on theaverage time interval, whether the electrode has a lateral/posteriorposition or an anterior position.
 3. The system of claim 1, wherein theelectrode is located in a coronary sinus vein branch of the leftventricle, and wherein the processing device is configured to determine,based on the average time interval, whether the electrode has alateral/posterior vein branch position or an anterior vein branchposition.
 4. The system of claim 1, wherein the first electrical eventcomprises atrial activity and the second cardiac electrical eventcomprises a peak of a QRS complex at the electrode.
 5. The system ofclaim 1, wherein the first cardiac electrical event comprises an onsetof a QRS complex and the second electrical event comprises a peak of aQRS complex sensed at the electrode.
 6. The system of claim 1, whereinthe first electrical event comprises a peak of a right ventricle QRScomplex occurring before or after the second electrical event and thesecond electrical event comprises a peak of a QRS sensed at theelectrode.
 7. The system of claim 1, wherein the processing device isconfigured to receive a first cardiac electrical signal from a firstdetection device and a second cardiac electrical signal from a seconddetection device.
 8. The system of claim 7, further comprising a secondelectrode configured for positioning in an atrium area of the patient'sheart, the processing device receiving a first cardiac electrical signalfrom the second electrode representing the first electrical event in theatrium area of the heart prior to the processing device receiving thesecond cardiac electrical signal representing the second electricalevent, the second electrical event comprising a left ventricle QRScomplex peak.
 9. The system of claim 7, further comprising a secondelectrode configured for positioning in a right ventricle area of thepatient's heart, the processing device receiving a first cardiacelectrical signal from the second electrode representing the firstelectrical event in the right ventricle before or after the processingdevice receiving the second cardiac electrical signal representing thesecond electrical event, the second electrical event comprising a leftventricle QRS complex peak.
 10. The system of claim 1, furthercomprising a means for adjusting one or more settings of a VRT devicebased on a determined position of the electrode.
 11. A system fordetermining the position of an electrode in a patient's heart, thesystem comprising: an electrode; and a processing device configured toreceive a first cardiac electrical signal representative of a firstelectrical event sensed repeatedly by the electrode over a time windowspanning a plurality of heartbeats and a second cardiac electricalsignal representative of a second electrical event repeatedly sensed bythe electrode over the time window, and to calculate a position of theelectrode in or near the heart based at least in part upon a comparisonof an average time interval between the first and second electricalevents during each heartbeat within the time window to a thresholdvalue; and wherein the processing device is configured to determine,based on the average time interval, whether the electrode has alateral/posterior position or an anterior position.
 12. The system ofclaim 11, wherein the electrode is located in a coronary sinus veinbranch of the left ventricle, and wherein the processing device isconfigured to determine, based on the average time interval, whether theelectrode has a lateral/posterior vein branch position or an anteriorvein branch position.
 13. The system of claim 11, wherein the firstelectrical event comprises atrial activity and the second cardiacelectrical event comprises a peak of a QRS complex at the electrode. 14.The system of claim 11, wherein the first cardiac electrical eventcomprises an onset of a QRS complex and the second electrical eventcomprises a peak of a QRS complex sensed at the electrode.
 15. Thesystem of claim 11, wherein the first electrical event comprises a peakof a right ventricle QRS complex occurring before or after the secondelectrical event and the second electrical event comprises a peak of aQRS sensed at the electrode.
 16. The system of claim 11, wherein theprocessing device is configured to receive a first cardiac electricalsignal from a first detection device and a second cardiac electricalsignal from a second detection device.
 17. A method for determining aposition of an electrode located in a ventricle area of a patient'sheart, the method comprising: detecting a first depolarization for eachof a plurality of intracardiac depolarization wavefronts sensed by theelectrode over a time window spanning a plurality of heartbeats;detecting a second depolarization event for each of the plurality ofintracardiac depolarization wavefronts sensed by the electrode over thetime window; measuring a plurality of first time intervals between thefirst depolarization event and the second depolarization event occurringduring each heartbeat within the time window; computing an average timeinterval based on the first time intervals measured over the timewindow; and determining from the average time interval whether theelectrode has a lateral/posterior position or an anterior positionwithin the ventricle area.
 18. The method of claim 17, whereindetermining whether the electrode has a lateral/posterior position or ananterior position within the ventricle area comprises comparing theaverage time interval to a threshold value and determining alateral/posterior position when the average time interval is greaterthan the threshold value.
 19. The method of claim 17, wherein detectingthe first depolarization event comprises sensing a peak or onset of aQRS complex.
 20. The method of claim 17, wherein detecting the seconddepolarization event comprises sensing a peak or onset of a QRS complex.